DA-03 · LESSON 02

Deposit and withdraw

KEY DEFINITIONS

Terms used in this lesson

Collateral: An asset pledged against a debt; it can be used to cover the debt if agreed conditions are breached.
Vault: A set of Bitcoin outputs and spending rules that holds collateral and represents the current loan state.
UTXO: Unspent transaction output: one discrete chunk of bitcoin that can be used as a transaction input.
BTC: The common market ticker for bitcoin.
UNIT: Ducat’s dollar-pegged stablecoin, the asset a borrower can create against bitcoin collateral.
Outpoint: A transaction ID plus output number that identifies one exact prior output.
Guardian: A Ducat policy-checking signer that can authorize or reject defined protocol transactions.

Collateral changes consume the current vault UTXO and create a successor while validation enforces allowed value and ratio transitions.

45 min Difficulty 4/5 Not started

VISUAL MODEL

See the whole mechanism before going step by step

Use the diagrams to orient yourself. Then the guided explanation below teaches every part in depth.

4 explanatory views

CONCEPT-SPECIFIC MAP · ducat vaultA Ducat action moves one Bitcoin-anchored vault state to a successorSelect any state to inspect its exact role.

RELATIONSHIP MAPInputs, rule, and outputs

01
PREDECESSORCurrent vault outpoint
The current Bitcoin output anchors collateral and identifies the state being spent.
02
REQUESTDeposit and withdraw
The Deposit and withdraw workflow proposes one exact action and successor state.
03
POLICYProfile, oracle, signatures
Applicable policy, price evidence, authorization, and transaction shape are checked.
04
BITCOIN SPENDScript-valid transaction
Bitcoin miners and nodes can include only a transaction that satisfies Bitcoin rules.
05
SUCCESSORNew outpoint and state
Ducat validators reconstruct debt, collateral, token, and account changes from the confirmed transaction.

Rule shown: Bitcoin checks the spend; Ducat components independently reconstruct and validate the additional protocol state.

STAGE 1 OF 5PREDECESSOR: Current vault outpoint

The current Bitcoin output anchors collateral and identifies the state being spent.

Governing relationship: Bitcoin checks the spend; Ducat components independently reconstruct and validate the additional protocol state. Complete path: 1. PREDECESSOR, Current vault outpoint. The current Bitcoin output anchors collateral and identifies the state being spent. 2. REQUEST, Deposit and withdraw. The Deposit and withdraw workflow proposes one exact action and successor state. 3. POLICY, Profile, oracle, signatures. Applicable policy, price evidence, authorization, and transaction shape are checked. 4. BITCOIN SPEND, Script-valid transaction. Bitcoin miners and nodes can include only a transaction that satisfies Bitcoin rules. 5. SUCCESSOR, New outpoint and state. Ducat validators reconstruct debt, collateral, token, and account changes from the confirmed transaction.

1. State transitionWhat exists, what changes, and what results

BEFORE

Start with 1 BTC, 50,000 UNIT debt, an illustrative 80,000 dollar BTC price, and a 150 percent displayed minimum. Required practice uses another vector.

MECHANISM

The client selects the current vault outpoint and debt rather than a stale earlier version.

AFTER

A stale current outpoint fails at Bitcoin; a changed debt or recipient fails the Ducat transition even when the ratio is high. Required practice uses a separate server-execut…

Text equivalent: Starting from Start with 1 BTC, 50,000 UNIT debt, an illustrative 80,000 dollar BTC price, and a 150 percent displayed minimum. Required practice uses another vector. The mechanism begins when The client selects the current vault outpoint and debt rather than a stale earlier version. The resulting lesson is A stale current outpoint fails at Bitcoin; a changed debt or recipient fails the Ducat transition even when the ratio is high. Required practice uses a separate server-executed vector.

2. Mechanism pathSelect a stage to inspect its job

STAGE 1 OF 4

Read the live vault

The client selects the current vault outpoint and debt rather than a stale earlier version.

Complete path: 1. Read the live vault: The client selects the current vault outpoint and debt rather than a stale earlier version. 2. Apply the collateral differential: Deposit adds wallet BTC; withdraw assigns allowed BTC to an owner-controlled output. 3. Create the successor: The new vault output retains the debt while committing the changed collateral state and required spending paths. 4. Validate direction and ratio: Guardian and protocol checks confirm the requested differential, output shape, authorization, fees, and post-action collateral constraints.

3. Rule and failure boundaryWhat accepts the result and where it can stop

ACCEPTED PATH

The worked case executes the named inputs and checks in the displayed order. Guardian and protocol checks confirm the requested differential, output shape, authorization, fees, and post-action collateral constraints.

CHANGED CONDITION

A missing, malformed, stale, unauthorized, or inconsistent required input stops at its first named boundary. Both are vault state transitions with action-specific successor and policy checks, not arbitrary movements from a normal address.

Important distinction: A deposit and withdrawal are opposite ordinary wallet payments. Both are vault state transitions with action-specific successor and policy checks, not arbitrary movements from a normal address.

Text equivalent: The accepted path is enforced by The worked case executes the named inputs and checks in the displayed order. Guardian and protocol checks confirm the requested differential, output shape, authorization, fees, and post-action collateral constraints. If the required condition changes, A missing, malformed, stale, unauthorized, or inconsistent required input stops at its first named boundary. Both are vault state transitions with action-specific successor and policy checks, not arbitrary movements from a normal address.

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Learn the idea

Deposit adds bitcoin collateral to a live vault. Withdraw removes some collateral. Both consume the current vault UTXO and create a successor; withdrawal must remain within the active collateral policy.

GUIDED EXPLANATION1/4 ideas inspected

Read the live vault

The client selects the current vault outpoint and debt rather than a stale earlier version.

The worked example follows the explanation

Inspect every idea above to open it.

Important distinction“A deposit and withdrawal are opposite ordinary wallet payments.”

Both are vault state transitions with action-specific successor and policy checks, not arbitrary movements from a normal address.

FINISH LEARNING FIRST

The questions unlock after every required learning activity

Inspect every guided idea, open the worked example, rebuild its mechanism, and complete the deterministic lesson tool. Your progress is saved automatically.